Pitchblende contains a small amount of radium as a radioactive decay product of uranium. Because the uranium isotopes 238U and 235U will decay to form the leadisotopes206Pb and 207Pb, pitchblende also always contains small amounts of lead. Small amounts of helium are also present in pitchblend as a result of alpha decay. Helium was first found on Earth in pitchblende after having been discovered in the Sun's atmosphere.